In recent years, a light source unit including a fluorescent structure such as a phosphor wheel has been used for a projection display apparatus (projector) (see PTL 1, for example). The phosphor wheel includes a plurality of phosphors on a substrate, for example, and the plurality of phosphors are fixed to the substrate by a binder. A portion of excitation light having entered the fluorescent structure is absorbed by the phosphors and is converted into fluorescence, whereas a remaining portion of the excitation light passes through the fluorescent structure without undergoing the conversion (transmitted light).